Electrolytic apparatus



2 Sheets-Sheet 1 FiG. 2

FIG. 4

W` J. MAHANY ELECTROLYTI C APPARATUS FIG. 1

July 1l, 1967 Filed Aug. 14, 1962 INVENTQR wlLLlAM J. MAHANY ATToRmP/,Z`

July 11, 1967 w. J. MAHANY 3,330,755

ELECTROLYTI C APPARATUS Filed Aug. 14, 1962 2 sheets-sheet 2 IN VEN TOR. WILLIAM J. MAHANY FIG. 5 @Y ATTORNEY United States Patent C) 3,330,755 ELECTROLYTIC APPARATUS William J. Mahany, Canandaigua, N.Y. assignor to Electro-Cell Corporation, Canandaigua, N.Y., a corporation of N ew York Filed Aug. 14, 1962, Ser. No. 216,799 3 Claims. (Cl. 204-230) This invention relates to novel apparatus for producing gases by electrolytic decomposition of a liquid, and more particularly to apparatus for producing oxygen and hydrogen by the electrolytic decomposition of water. In a still more specific aspect the invention relates to novel apparatus of this type which is of relatively compact and portable construction and especially suitable for economical use in applications where only relatively small quantities of gases are required.

Previously known electrolytic apparatus for producing oxygen and hydrogen have been relatively bulky, and complex both in construction and operation. Accordingly, they have not been suitable for point-of-use installation, especially in applications where only relatively small quantities of the gases are desired. `Most small consumers of oxygen and hydrogen have heretofore preferred to buy the gases in pressure cylinders and to replace the cylinders as they become empty. Such cylinders are, however, heavy and diiiicult to handle. They are, moreover, difcult to store and are a safety hazard. Furthermore, the consumer has to pay not only for the gas used, but for the cost of compressing the gas so that it can be packed in a cylinder, for the handling of the cylinder, of storing it before and after use, and of returning it when empty.

One important object of the present invention is to provide novel, economical electrolytic apparatus for producing gases such as hydrogen and oxygen, and more particularly to provide apparatus of this type which is especially suitable for point-of-use installation in situations where only moderate, or small quantities of the gases are required.

Another object of the invention is to provide apparatus of the character described which is capable of fully automatic operation, producing hydrogen and oxygen on demand as required.

Another object is to provide apparatus of this type which is fully automatic, yet of relatively simple and inexpensive construction, highly dependable, and troublefree and long-lasting in service.

A further object of the invention is to provide apparatus of the character described which includes a relatively simple and trouble-free pressure balancing system to keep the oxygen and hydrogen under equal pressures, thereby to prevent inadvertent mixing of the two gases within the electrolyzer and to insure continuous trouble-free operation.

Another object is to produce apparatus of this type which includes a novel, highly sensitive, pressure differential sensor for detecting a pressure differential between the cathodic and the anodic outputs of the electrolyzer, and automatic means responsive to the sensor for limiting any such pressure differential to relatively small values.

Still another object of the invention is to provide apparatus of the character described which lis readily transportable, but which, if desired, may be placed in a central location and its output piped to utilization points.

The foregoing and other objects and advantages of the invention will become apparent from the following detailed description of a representative embodiment thereof, taken in conjunction with the drawing, wherein:

FIG. 1 is a vertical sectional view of the electrolyzing 323,755 Patented July 11, 1967 tankof apparatus built according to a presently preferred embodiment of the invention;

FIG. 2 is a horizontal sectional view taken along the line 2 2 of FIG. 1, looking in the direction of the arrows;

FIG. 3 is a schematic diagram of the hydraulic and pneumatic circuits of the apparatus;

FIG. 4 is a vertical sectional View of the pressure differential sensing device, which is incorporated in the apparatus as shown in FIG. 3; and

FIG. 5 is an electrical schematic diagram of the electrical operating and control portion of the apparatus.

Briefly, the apparatus of the present invention includes a pressure tank for containing an electrolytically decomposable liquid, such as water, a pump for feeding the liquid into the tank, accumulators for storing the gases produced by electrolysis in the tank, pressure equalization means for preventing the buildup of a pressure differential between the two accumulators, and a relatively simple system of automatic controls to achieve fully automatic, failsafe operation of the apparatus.

The pressure equalization means includes a pair of electrical probe chambers connected respectively to the anodic and cathodic gas output sides of the electrolyzer tank, and through a flow-restrictive device to each other. The chambers are partly iilled with an electrically conductive liquid, and a probe extends downwardly within each charnber for contacting the liquid whenever it is above a predetermined level therein. Even a relatively small pressure differential between the outputs of the electrolyzer drives the liquid downwardly in one chamber lbelow the lower end of the probe in that chamber, thereby breaking an electrical circuit to produce an electrical signal in response to the pressure differential. The sensor is extremely sensitive, yet fully reliable and dependable in operation. Means responsive to the sensor are provided for venting the relatively higher pressure output of the electrolyzer, thus to limit the pressure differential to a relatively small value.

Referring now to the drawings, and first to FIG. l, the apparatus shown includes an electrolyzing tank, or generator unit 10 comprising an outer steel tube or cylinder 12 and an inner steel tube or cylinder 14, The tubes 12 and 14 function as the cathode -and the anode, respectively, of the electrolyzer unit. The walls of these tubes should be of equal thickness.

The opposite ends of the outer tube or cylinder 12 are closed .by plastic insulating plates, or discs 16 and 18, respectively, which seal .against the inner wall of the tube. The lower disc 16 is supported -by a lower reinforcing plate 20, which may be made of steel molded to the plastic disc 16 and which is welded, or otherwise rigidly secured within the outer tube or cylinder 12 near the lower end thereof. The upper insulating disc 18 is retained in place by a steel cover plate 22, which is molded to plastic disc 18 and which is removably .secured to the outer tufbe 12 by bolts 24, as shown, or by any other desired means. The bolts 24 extend through the cover plate 22 and through a ange 26, which is welded to and extends exteriorly around the outer tube or cylinder 12 at the upper end thereof.

The inner surface 28 of the outer tube 12 and the outer surface 30 of the inner tube 14 are preferably threaded for their full heights, as `shown Vat 31 and 33 and their threaded portions are preferably rough sand blasted or otherwise corrugated or `st-riated in order to increase their effective areas. The threads are preferably nickel plated for greater conductivity.

A porous, tubular separator or diaphragm 32, which may be, for example, of woven asbestos and preshrunk, is supported between the outer tube 12 and the inner tube 14 upon annular, axially extending collars 34 and 36, respectively, which are integral with the respective end plates 16 and 18. The inner tube 14 ts loosely inside the collars 34 and 36; and `there is adequate clearance between the inner tube 14 and the upper collar 36 to permit gases generated during electrolysis to pass freely between this inner tube 14 and the upper collar 36.

A pair of coaxially arranged tubular ducts 42 and 44 are sealed through the lower insulating disc 16. The inner duct 42 is connected to a pipe 43 and serves -as the liquid inlet to conduct water into the ygenerator unit. The outer tube 44 is of larger bore diameter than the outside diameter of tube 42 so that there is space between it and the outside of tube 42. It is provided with a plurality of ports 45 and serves to connect the electrolyzer through a pipe 47 to a liquid level sensor yand indicator 84 (FIG. 3). The reinforcing plate 20 is apertured to :provide clearyance for the duct 44 without making electrical contact with it.

Electrically conductive plates or straps 38 and 40, respectively, are threaded into the opposite ends of the inner, anode tube 14, or otherwise conductively secured thereto, to effect a relatively low resistance electrical connection to it. The plates 38 and 40 are welded, or otherwise conductively secured to relatively heavy electrical leads or terminals 46 and 48, respectively, which are sealed `through the lower and upper insulating plates 16 and 18, respectively, and which serve as electrical input terminals for the inner cylinder 14. A tubular steel insert 49, which is molded into the plastic disc 18, and a nut 51 which is `threaded on the upper anode terminal 48, serve to secure this terminal in place.

The upper annular collar 36 is spaced inwardly from the outer tube 12 to allow gas generated during electrolysis to pass upwardly between the collar 36 and the tube 12.

A first outlet pipe 50 is molded into and sealed through the upper insulating plate 18 and opens interiorly in the :annular space between the upper annular collar 36 and the outer tube 12. A `second outlet pipe 52 is also molded into and sealed through the upper insulating plate 18 and opens interiorly within the annular collar 36.

For operation, a solution of sodium, potassium or lithium hydroxide or other highly conductive liquid is placed within the electrolyzer unit 10, and water is admitted through the inlet 42 iilling the inner and outer cylinders 14 and 12 to ya height determined by the liquid level sensor and indicator 84 (FIG. 3). The water ows from cylinder 14 into cylinder 12 through the groove 53 in plate 16 and through the porous 'baffle 32. The groove 53 extends under the lower end of tube 14. Instead of a groove, holes may be provided in the lower end of tube 14. Lithium hydroxide will minimize foaming. The terminals 46 and 48 of the inner `cylinder are connected to the anode of a lbattery or other source of unidirectional electric current, and the outer cylinder 12 is connected to the cathode. Electrical connections to the outer tube 12 may be made by means of conductive bands or Straps 54 tightened around this tube at axially spaced intervals therealong and connected by jumpers to the terminal cathode connectors 55.

The water of the yelectrolyte is decomposed by the current owing between the outer cylinder 12 and the inner cylinder 14, forming oxygen, and hydrogen. The oxygen flows upwardly along the outer surface of the inner cylinder 14 into the region 56 within the upper annular ange 36 and exhausts through the inner outlet nipple 52. The hydrogen forms along the inner surface 28 `of the outer cylinder and flows upwardly therealong into the space between the outer 4cylinder 12 and the annular flange or collar 36 and exhausts through the outer outlet nipple 50. The nipples are connected :by piping to the respective oxygen and hydrogen storage tanks where the gases are available for use.

The surface level of the electrolyte is kept above the lower edge of the upper flange or collar 36 so that the ange or collar 36 acts to seal the oxygen and hydrogen apart in their two separate outlet regions. Any pressure differential that may develop between the oxygen and hydrogen outlet regions is Controlled by means to be described hereinafter so that the electrolyte remains above the lower edge of the flange or collar 36 on both sides of the flange.

The hydraulic and pneumatic connections for the apparatus are shown in FIG. 3. Water is supplied through an inlet 62 which is preferably connected to a supply of preferably distilled water. This supply line is connected through a oat-operated safety switch 60 to the pipe 64 which is connected to a pump 66. The float-operated safety cut-off switch 60 is included for cutting off operation of the apparatus in the event of failure of the water supply. The outlet of the pump 66 is connected through a check valve 70 to the inlet 43 of the electrolyzer unit 10.

The anodic outlet 52 of the electrolyzer unit is connected through piping 71, 73, a flow control valve 72, and a check valve 74 to an oxygen storage tank 76. A trap 78 and a drain valve 80 are also connected to the anode outlet 52 for removing moisture and other impurities from the oxygen. The anodic outlet 52 is also connected by piping 82 to the upper end of a double throw, liquid-level operated switch 84, the lower end of which is connected to the inlet 47 at the bottom of the electrolyzer 10. The oat-operated switch 84 controls the energization of the pump motor 66 to maintain the desired level of the electrolyte within the electrolyzer unit 10.

The cathodic outlet 50 is connected through piping 81, 83, a ilow control valve 86, and a check valve 88 to storage tanks 90 and 92. As shown, twice the storage capacity is provided for the cathode output (hydrogen) as for the anode output (oxygen). The relative capacities of the storage tanks 76, 90 and 92 would normally be selected on the basis of the expected demand for each particular installation. In those installations wherein it is desired to provide primarily oxygen and relatively little hydrogen, or no hydrogen, the oxygen storage tank 76 is preferably made relatively large, and the hydrogen storage tanks 90 and 92 may be replaced by a relatively small accumulator, or ballast tank (not shown) which would serve primarily to reduce undesired, sudden pressure changes in the system. A trap 94 and a drain valve 96 are also connected to the cathode outlet 50 to remove water vapor and other impurities that may be carried by the cathode gas out of the electrolyzer 10.

A pressure differential sensor 100 is connected between the anode and cathode outlets 52 and 50, respectively, for detecting pressure differences between the cathode and anode gases in the electrolyzer.

As shown in detail in FIG. 4, the sensor 100 includes a pair of sealed vessels 102 and 104, which are partially lled with a conductive fluid 106 and are connected together at their lower ends through a flow restrictive needle valve 108, or any other desired ow restrictive device. A lill pipe 110 is connected to the lower ends of the vessels 102 and 104 for introducing the conductive fluid 106 into them. This tube is normally stoppered during operation. Gas inlet tubes 112 and 114, which are connected through tubing 83, '73, respectively, to the respective outlets 50 and 52 of the electrolyzer 10, are sealed through the upper ends of the vessels 102 and 104.

A differential in gas pressure at the electrolyzer outlets 50 and 52 thus causes a corresponding differential in the levels of the electrolyte 106 in the respective vessels 102 and 104. When there is no pressure differential, that is, when the pressure within the electrolyzer 10 is the same at the anode outlet 52 as at the cathode outlet 50, the electrolyte 106 stands at the same level in both of the vessels 102 and 104.

The side Walls 103, 105 of the vessels 102 and 104 are preferably made of glass or clear plastic for sighting and are encased in brass sleeves 107, 109 which have vertically disposed openings in them to permit viewing and checking the level of liquid in the vessels. Electrically conductive probes 116 and 118 extend downwardlyfrom the upper ends of the vessels 102 and 104, terminating a relatively short distance below the normal level of the electrolyte 106 in the respective vessels. Electrical control circuits are connected between the probes 116 and 118 and the lower ends of the vessels 102 and 104, as described hereinafter, for actuating means to limit any pressure differential that may develop to a relatively small value. A pressure differential may develop relatively rapidly, for example, when only one gas, say oxygen, is drawn from the apparatus for use. Resistors 120 and 122 are connected to the probes 116 and 118 and have their lower leads (not separately designated) extending into the electrolyte solution 106 in order to minimize the danger of sparking particularly on the hydrogen side at times when contact is broken between the probes 116 and 118 and the electrolyte 106.

The electrical control circuit is shown in FIG. 5. The electrolyzing current is supplied to electrolyzer unit from a first source 130 of electric current through a main disconnect switch 132, a pair of normally-open relay contacts RE-Za and RE-Zb, when closed, a transformer 134, and a full wave rectifier 136. An ammeter 138 and a voltmeter 140 may be provided for conventional control purposes. Because of the amount 0f power that may be required for electrolysis, this first source 130 is preferably of relatively high voltage such as a 220 or 440 volt, 60 cycle source.

As shown, the operating control portion of the circuit is arranged for connection to a conventional 110 Volt, 60 cycle source 142 of electric current. A two-pole disconnect switch 144 is connected in series with the main power lines 146 and 148, and the motor 150 of the pump 66 is connected between the lines 146 and 148 through two relay contacts RE-1a and RE-lb. The operating coil RE-l of the relay is connected also between the lines 146 and 148 in series with another relay contact RE-Sa. Closing of the relay contact RE-Sa energizes the relay RE-l, which thereupon closes its contacts RE-la and RE-lb to energize the pump motor 150 to drive the pump 66 thereby to force water into the electrolyzer 10.

The balance of the control circuit, in order to minimize the possibility of arcing in the system, is preferably operated at a relatively low voltage such as 12 or 24 volts. A voltage reducing transformer 152 is, therefore, connected between the input lines 146 and 148. Subsidiary power lines 154 and 156 are connected to the output of this transformer 152.

Energization of the electrolyzing circuit is effected by actuation of the first relay RE-Z, which is connected in series with four switches 68, 84-a, 158, and 160 between the low voltage power lines 154 and 156. When the relay RE-Z is energized, it closes its contacts RE-Za and RIE-2b, thereby enabling energization of the main electrolyzing power transformer 134, and, during times when the main power switch 132 is closed, initiating electrolysis within the electrolyzer 10, and maintaining continuous electrolysis so long as the main power switch 132 and the relay contacts RIE-2a and RIE-2b remain closed.

Of the four protective switches in series with the relay RIE-2, the first one 60 is the safety oat switch. This float switch is normally held closed during operation of the apparatus, and opens only when the water level is reduced, as may occur due to failure of the water supply. The second switch 84a is the low level contact of the level control switch 84 (FIG. 3) and is held closed during operation of the apparatus so long as there is sufficient electrolyte within the electrolyzer 10. The other two switches 158 and 160 are pressure overload switches con- 6 nected in the supply lines between the respective electrolyzer outlets 50 and 52 and the storage tanks 76, and 90 and 92. These switches 158 and 160 are normally closed, but they open in response to internal pressures within the system above a predetermined limit.

It will be seen, therefore, that the relay RE-2 is normally continuously energized during operation of the apparatus, holding its contacts RE-Za and RE-2b continuously closed to provide power to the electrolyzer 10. The relay RE-2 becomes deenergized, thereby opening its contacts REZ-2a and RE-Zb to stop the electrolysis, upon the occurrence of any of the following events: (a) failure of the Water supply, (Ib) lowering of the electrolyte level within the electrolyzer 10 below a predetermined level, which is preferably set at some level above the lower edge of the upper annual flange 36 (FIG. l) and, (c) excessive gas pressure in either of the supply lines connecting the electrolyzer outputs 50 and 52 to the storage vessels 76, and and 92.

The next relay RE-S is connected fbetween the low voltage supply lines 154 and 156 in series with the second, high-level, contact 84-b of the water level control switch 84. The contact RE-3a of this relay is in series with the pump motor control relay RE-l for indirectly controlling energization of the pump motor 150. The switch contact 84-Kb is held upon so long as the electrolyte level in the electrolyzer 10 is above a predetermined limit, and closes when the electrolyte falls below that limit, the limit being chosen so that the second contact 84-b closes at a higher electrolyte level than the level required for opening of the first contact 84-a. In operation, therefore, the pump motor is alternately energized and deenergized, and functions to maintain the electrolyte in the electrolyzer 10 at a level above the emergency cut-off level, which is the level at which the low-level contact 84-a of the level control switch opens. Thus, the electrolysis is enabled to continue uninterruptedly.

The last two relays RE-A. and RE-S are connected across the low voltage supply lines 154 and 156 in series with the electrolyte 106 and with the respective probes 116 and 118 of the pressure differential sensor. As hereinabove described, the probes act similarly to float switches in that they are connected in series with the electrolyte 106 in electrical circuits which become alternately open and closed in response to changes in the level of the electrolyte within the respective vessels 102 and 104. The contacts RE-4a and RE-Szz of the respective relays RIE-4 and RE-S are normally closed. When the electrolyte 106 contacts both probes 116 and 118, the circuits to the relays RE-4 and RE-S are closed and Iboth relays REZ-4 and REPS are energized and hold their contacts REI-4a and RE-Sa open. When the relays RE-4, RE-S become deenergized their contacts RE-4zz and RE-Sa close. The closing of these contacts complete the circuits to the respective solenoids 164 and 166 of two solenoid-operated pressure release valves 165 and 167, which are connected, respectively, in the lines between the outlets 50 and 52 of the electrolyzer and the storage tanks 76, 90 and 92. The relays RE-4 and RE-5 operate to vent whichever one of the outlets 50 or 52 has a higher pressure than the other, thereby maintaining substantially equal pressures at the two outlets 50 and 52 of the electrolyzer.

The apparatus described is relatively cheap to manufacture because the cylinders 12 and 14 can be made from tubing utilizing plastic end plates 16 and 18. Through use of an asbestos separator or baille, moreover, the unit operates more efficiently since the electrolyzing current is not being passed through as much water. Furthermore the generator cell 10 has only two openings at the bottom and three at the top, thus minimizing machining and fitting.

While the invention has been described in connection with a specific embodiment thereof, it will be understood that itis capable of further modication, and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles 7 of the invention and including such departures from the present disclosure as corne within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth, and as fall within the scope of the invention or the limits of the appended claims.

Having thus described my invention, what I claim is:

1. A compact gas generating apparatus comprising (a) an electrolyzer having an inlet for admitting a liquid, which is to be electrolytically decomposed, and two outlets for releasing, respectively, anodic and cathodic gaseous decomposition products of the liquid, and

(b) pressure equalization means for equalizing the gas pressures in said electrolyzer at said outlets, said presmined limits.

(c) a first vessel connected to one of said outlets,

(d) a second vessel connected to the other one of said outlets,

(e) means including a ow restrictive device connecting said second vessel to said rst vessel,

(f) an electrically conductive liquid partly filling 'both of said vessels, and

(g) electrical probes extending downwardly within said vessels toward said liquid, whereby a relatively slight differential between the pressures within said electrolyzer at said outlets will effect a differential in liquid level within said vessels so that the probe in one of said vessels contacts the liquid therein and the probe in the other one of said vessels is out of contact with the liquid therein,

(h) solenoid actuated vent valves connected respectively to said outlets, and

(i) electrical circuit means for selectively energizing said vent valves in response to the making of contacts between said probes and said liquid thereby to vent the one of said outlets at which the pressure in said electrolyzer is relatively higher.

2. A compact gas -generating apparatus suitable for easy portability comprising (a) an electrolyzer having an inlet for admitting a liquid, which is to be electrolytically decomposed into constituent gases, and two gas outlets, said electrolyzer including (b) a pair of normally vertical, coaxially arranged, electrically conductive tubes, insulating end plates sealed to the outer one of said tubes and supporting the inner one thereof, and

(c) a porous cylindrical diaphragm supported by said end plates -between said tubes,

(d) said outlets opening within said outer tube on opposite respective sides of said diaphragm,

(e) inlet means opening within said inner tube near the lower end thereof for admitting a liquid to be electrolyzed,

(f) means for supplying liquid to be electrolyzed,

(g) a pump for forcing liquid from said supply means into said electrolyzer under pressure,

(h) a liquid-level actuated switch for controlling operation of said pump,

(i) gas storage containers connected separately to said outlets for storing the gaseous decomposition products of the liquid electrolyzed in said electrolyzer,

(j) a pressure differential sensor connected between said outlets for selectively producing one of two 8 electrical signals in response to a pressure dierential in said electrolyzer between said outlets, one of said two signals indicating a relatively higher pressure at one of said outlets, and the other of said two signals indicating a relatively higher pressure at the other outlet,

(k) means responsive to said sensor for selectively venting said outlets thereby to reduce such pressure differential,

(l) and a liquid level sensing device for `alternately energizing and deenergizing said pump in response to variations of liquid level within said electrolyzer, thereby to maintain the liquid level within predetermined limits.

3. A compact gas generating apparatus comprising (a) an electrolyzer having an inlet for admitting a liquid, which is to be electrolytically decomposed, and two outlets for releasing, respectively, anodic and cathodic gaseous decomposition products of the liquid, and

(b) pressure equalization means for equalizing the gas pressures in said electrolyzer at said outlets, said pressure equalization means including (c) a first vessel connected to one of said outlets,

(d) a second vessel connected to the other one of said outlets,

(e) uid conducting means connecting said second vessel to said first vessel,

(f) an electrically conductive liquid partly lling both of said vessels, and

(g) electrical probes extending downwardly within said vessels toward said liquid, whereby a relatively slight differential between the pressures within said electrolyzer at said outlets will eiect a diterential in liquid level within said vessels so that the probe in one of said vessels contacts the liquid therein and the probe in the other one of said vessels is out of contact with the liquid therein,

(h) solenoid actuated vent valves connected respectively to said outlets, and

(i) electrical circuit means for selectively energizing -said vent valves in response to the making of contacts between said probes and said liquid thereby to vent the one of said outlets at which the pressure in said electrolyzer is relatively higher.

References Cited UNITED STATES PATENTS 1,322,417 11/ 1919 Fischer 204-260 1,819,917 8/ 1931 Niederreither et al. 204-129 1,842,703 1/ 1932 Vorce 204-260 1,856,663 5/1932 Smith 204-280 X 2,349,998 5/1944 Trinius 204-260 2,393,201 1/1946 Statord 200-81.6 2,470,073 5/ 1949 Low 204-266 2,520,624 8/1950 Davey 20G-81.6 X 2,695,874 11/ 1954 Zdansky 204-258 2,825,781 3/1958 Mitchell 20G-81.5 2,846,384 8/ 1958 Denora 204-266 X JOHN H. MACK, Primary Examiner. HOWARD s. WILLIAMS, Examiner. A. B. CURTIS, W. VAN SISE, Assistant Examiners. 

1. A COMPACT GAS GENERATING APPARATUS COMPRISING (A) AN ELECTROLYZER HAVING AN INLET FOR ADMITTING A LIQUID, WHICH IS TO BE ELECTROLYTICALLY DECOMPOSED, AND TWO OUTLETS FOR RELEASING, RESPECTIVELY, ANODIC AND CATHODIC GASEOUS DECOMPOSITION PRODUCTS OF THE LIQUID, AND (B) PRESSURE EQUALIZATION MEANS FOR EQUALIZING THE GAS PRESSURES IN SAID ELECTROLYZER AT SAID OUTLETS, SAID PRESMINED LIMITS. (C) A FIRST VESSEL CONNECTED TO ONE OF SAID OUTLETS, (D) A SECOND VESSEL CONNECTED TO THE OTHER ONE OF SAID OUTLETS, (E) MEANS INCLUDING A FLOW RESTRICTIVE DEVICE CONNECT-ING SAID SECOND VESSEL TO SAID FIRST VESSEL, (F) AN ELECTRICALLY CONDUCTIVE LIQUID PARTLY FILLING BOTH OF SAID VESSELS, AND (G) ELECTRICAL PROBES EXTENDING DOWNWARDLY WITHIN SAID VESSELS TOWARD SAID LIQUID, WHEREBY A RELATIVELY SLIGHT DIFFERENTIAL BETWEEN THE PRESSURES WITHIN SAID ELECTROLYZER AT SAID OUTLETS WILL EFFECT A DIFFERENTIAL IN LIQUID LEVEL WITHIN SAID VESSELS SO THAT THE PROBE IN ONE OF SAID VESSELS CONTACTS THE LIQUID THEREIN AND THE PROBE IN THE OTHER ONE OF SAID VESSELS IN OUT OF CONTACT WITH THE LIQUID THEREIN, (H) SOLENOID ACTUATED VENT VALVES CONNECTED RESPECTIVELY TO SAID OUTLETS, AND (I) ELECTRICAL CIRCUIT MEANS FOR SELECTIVELY ENERGIZING SAID VENT VALVES IN RESPONSE TO THE MAKING OF CONTACTS BETWEEN SAID PROBES AND SAID LIQUID THEREBY TO VENT THE ONE OF SAID OUTLETS AT WHICH THE PRESSURE IN SAID ELECTROLYZER IS RELATIVELY HIGHER. 